china is demanding more oil every day to power its growing economy. just as opec cut some of its output. and international sanctions are reducing the amount of iranian oil on the world market. at home, refineries are shutting down from maintenance as they prepare to switch to a summer blend. then market speculation and a weaker dollar play a role. in san diego -- >> hey, i'm a waitress. come on. i'm not making 200 grand a year. >> reporter: the price at the pump can quickly add to the cost of the daily commute. a 40-mile round-trip, 22 days a month, averaging 22 mpg at $3.50 a gallon costs $140 a month. at today's average of $3.73 a gallon, $149 a month. at $4.25 a gallon, $170. and at $4.50 a gallon, $180 a month. >> we have to work, so we keep coming to work every day. but you have to put gas in your car to come to work. >> reporter: 43 cents in a month. the national average, $3.73 right now. and the experts are saying they don't think that we will get over $4 a gallon for a national average. but california, illinois, will see over $4 and approachin